Sonic communication system



Sept. 22, 1964 J. E. FREEMAN some COMMUNICATION SYSTEM Filed Jan. 27 1958 2 Sheets-Sheet l /\2 l2 l3 ///O94 8 7 1 INVENTOR JEFF E. FREEMANATTORNEY Sept. 22, 1964 E. FREEMAN some COMMUNICATION SYSTEM Filed Jan.27, 1958 2 Sheets-Sheet 2 w Q. i J 1 INVENTOR JEFF E FREEMAN ATTORNEYUnited States Patent 3,1 9, SONIC QQMMUNICATION SYSTEM .leil E. Freeman,2727 Weaver St, Fort Worth, Tex. Filed Jan. 27, 1958, Ser. No. 711,437

4 (Ilaims. (Cl. 346-6) This invention relates to electrical soundsystems and more particularly to systems for producing or responding tounderwater sound. While not limited thereto, the invention isparticularly applicable to sound systems for use in connection withswimming pools.

A general object of the invention is to devise an improved electricalsystem -for selectively producing sound under water or detectingunderwater sound and reproducingthe same above water. In this regard,the invention is useful for producing underwater oral instructions forswimmers, for producing musical accompaniments for water ballets, andfor like purposes, the device also being capable of response tounderwater sound, as for warning purposes, or of reproducing underwatersounds.

Another object is to provide a novel, selectively operable,multi-purpose sound system for swimming pools and like applications.

A further object is to provide an electrical circuit incorporating anunderwater transducer which detects and determines when there has beenan increase and when there has been a decrease in pressure at thetransducer thus providing a means to maintain the water in a swimmingpool or tank at a .constant level or to maintain a submarine at apredetermined depth.

A further object is to provide an improved underwater transducer forsuch systems.

In order that the manner in which these and other objects are achievedin accordance with the invention can he understood in detail, referenceis had to the accompany drawings, which form a part of thisspecification, and wherein FIG. 1 is a sectional view, Withsome partsshown in elevation and with windings shown schematically for clarity, ofan underwater transducer constructed in accordance with the invention;

FIG. 2 is a schematic diagram illustrating one embodi ment of theinvention, and

FIG. 3 is a schematic diagram illustratinga second embodiment. a i

Referring now to FIG. 1, it will be seen that the invention includes atransducer indicated generally at 1 and cOmprising a solid body 2 inwhich is partially embedded a U-shaped permeable core 3. The body 2 isprovided at one face with a recess 2 the ends .of the legs of core 3extending out of the-body into the recess. 'Onone leg of the core 2 iswound a coil 4 embedded completely in body 2. Disposed betweenthelegs ofcore 3 and extending parallel thereto is a permanent magnet 5, to thetip of which is secured a permeable cored on which is wound a secondcoil 7.

Disposed within recess 2 and extending thereacross is a plate 3 ofpermeable material such as mild steel or soft iron. Provided with a fleajoint 9 adjacentits periphery,

the plate 8 is secured in place by means comprising an into gasket 11,which force clamps the periphery of perme- 3,l5,3i5 Patented Sept. 22,1964 its? able plate 8 between the gaskets. The combination of plate 8,gaskets 10, l1 and clamping plate 12 serves to seal the interior ofrecess 2 It will be noted that permeable plate 8 is spaced outwardlyfrom the tips of the legs of core 3.

When the transducer is placed below the surface of a body of water thepressure existing at the transducer, due to the water above thetransducer, will tend to move the plate 8 to a position which is closerto the tips of core 3. The combination of flex joint 9 and resilientgaskets ill, 11 permit the pressure present at the transducer to beefifective to so move plate 8.

At the face of the body 2 opposite permeable plate 8, there is partiallyembedded in the body a coupling or adaptor 14 via which insulatedconductors are led to coils 4 and 7. Thus, conductors i5, 16 areconnected to the terminals of coil 4, While conductors l7, 18 areconnected to the terminals of coil 7.

Body 2., with the elements 3-6 and 14 embedded or partially embeddedtherein, is advantageously formed by conventional casting proceduresfrom a suitable plastic material, such as wax or synthetic resincomposition.

It is of the utmost importance that the acoustic impedance of the movingsystem of the transducer 1 be accurateiy matched to that of the water.in this regard, the thickness of permeable plate 8, the flexibility ofjoint 9 and the compliance of gaskets ill, it must be carefully selectedto accomplish acoustic impedance matching.

To employ transducer 1 for producing underwater sound, an audiofrequency voltage is applied to coil 7, via conductors i7, 18, sochanging the magnetic flux density at the tip of core 6 in accordancewith the audio frequency of the voltage, resulting in a correspondingvibration of permeable plate 8.

The transducer 1 can be employed as a detector 6f underwater acousticenergy. The device is then employed as a microphone using the voltageinduced in coil 7 by the movement of the permeable plate 8 caused byunderwater acoustic energy.

One mode of employing the transducer 1 in accordance with the inventionis illustrated in the system embodiment shown in PEG. 2. Here, theinvention employs electrical circuit components indicated generally at Fand connected to transducer ii, the transducer being submerged in aswimming pool. The system comprises four ganged rotary selector switchesi 22 provided with movable contacts 2346, respectively. Each selectorswitch has four fixed contacts AD. The switches are so ganged that allfour rotary contacts engage like fixed contacts, that is, when one is inthe A position, all are in A position. The A, C and D contacts of switch19 are connected to ground through coil 27 of speaker 28. Contact B ofswitch 1% is connected to ground through resistor 29 and coil 27. Thepivotal end of contact arm 23 is connected to the output of audioamplifier 3%. Switch 19 thus provides a means for connecting'the outputof the amplifier. to speaker 23 for each position of movable con tact23. The output of amplifier 3b is also connected to contact B of switch21. The outputs of microphone 31, radio frequency detector 32 andphonograph pick-up 33 are connected to the fixed contacts of a switch34. The movable contact of selector switchfid is connected via resistor.35 to the A and contacts of switch 269. The movable contact of switch2% is 3 connected to ground via the resistance 36 of potentiometer 37.The adjustable contact 38 of the potentiometer is connected to the inputof audio amplifier St). The potentiometer 37 provides a means forvarying the level of input to the audio amplifier.

The lead 17 of coil '7 of the electromagnetic transducer 1 is connectedto contact C of switch 20 and is also connected to the movable contactof switch 21. Lead 18 of coil 7 of the transducer is connected toground.

Contact D of switch 21 is connected to ground via the primary winding 39of transformer at). One end of the secondary winding 41 is connected toground and the other end is connected through the grid current limitingresistor 42, to the grid of triode vacuum tube 43. The cathode of tube43 is connected to ground through the grid biasing resistor 44. Theplate of the triode is connected to ground via coupling capacitor 45 andgrid resistance 46. The plate is also connected via load resistance 47to contact D of switch 22.

The grid of a second triode vacuum tube 43 is connected, via gridcurrent limiting resistance 49, to the conductor which connectscapacitor 45 and resistance 46. The cathode of tube 48 is connected toground through the grid biasing resistor 51). The plate of this tube isconnected to ground via coupling capacitor 51 and grid resistance 52,and is also connected via load resistance 53 to contact D of switch 22.

The grid of a gas discharge tube 54, which in this embodiment is athyratron, is connected via grid limiting resistance 55 to the conductorwhich joins capacitor 51 and resistance 52. The plate of thyratron 54 isconnected to contact D of switch 22. The thyratron cathode is connectedto one end of resistance 56. The other end of resistance 56 is connectedto ground via capacitor 57. A gas discharge tube 58, which in thisembodiment is a neon tube, is connected in parallel with capacitor 57,the anode of the neon tube being connected to the conductor whichconnects resistance 56 to capacitor 57. The cathode of the neon tube isconnected to ground. The anode of neon tube 58 is also connected, viaseries-connected capacitor 5% and resistance 60 to contact D of switch29.

The cathode of thyratron 54 is also connected, via resistor 61, to themovable contact 62 of potentiometer 63. The resistance 64 of thepotentiometer 63 is connected between the D contact of switch 22 andground. The potentiometer 63 is used to adjust the bias of the thyratron54.

The B+ or plate supply voltage for tubes 43, 48 and 54 is connected tothe movable contact 26 of switch 22.

Operation of the system of FIG. 2 is as follows: First consider thesystem when the respective movable contacts of switches 19-22 are intheir A positions. Switch 34- can be positioned to select any one of thethree audio frequency sources 31-253. The audio signal so selected isapplied to the input of audio amplifier 30, with fixed resistor 35 andpotentiometer 37 controlling the magnitude of the input signal. Theoutput of the amplifier is supplied, via movable contact 23 and thecontact A of switch 19, to speaker 23. Thus, the system provides aloudspeaker operation for audio frequency signals obtainable from eithera radio frequency detector, microphone or phonograph pick-up.

When the movable contacts 23-26 are in their B positions, the system iseifectively connected as just described and, in addition, the output ofamplifier 30 is applied to the coil 7 of transducer 1 via contact 25.Application of the audio frequency signal to coil 7 causes the plate 8to vibrate correspondingly, resulting in audible transmission of theamplifier output to the medium surrounding the transducer.

Transducer 1 requires a greater operating voltage than does speaker 23.Accordingly, to maintain the speaker volume at a desired level, thesignal is now supplied to the speaker via resistor 29.

A third function of the system is provided when the movable contacts23-26 are in their C positions. The system now utilizes transducer 1 asa microphone with the signal amplified and supplied to speaker 28. Inthis case the lead 17 of coil 7 is connected to the input of audioamplifier 30 via movable contact 24 and input adjusting potentiometer37. The amplifier output is connected to the coil 27 of speaker 28 viamovable contact 23.

The fourth, or D positions of selector switches 19-22 provide a soundwarning system which is initiated by a disturbance of the watersurrounding the transducer, which functions now as a pick-up. Thevoltage induced in coil 7 by vibration of plate 8 is applied, viamovable contact 25, to the primary winding 39 of transformer 40. Theoutput of transformer 40 appears across the secondary winding 41 and isapplied to the first stage of the two-stage resistance-coupled audioamplifier indicated generally at E and hereinbefore described in detail.The B+ supply for the amplifier tubes is derived via movable contact 26.

The audio output of the second stage of amplifier E is applied acrossgrid resistor 52. The thyratron 54 is biased via the potentiometer 63,which is connected between ground and the B+ supply present at the Dcontact of switch 22. The audio output of the second stage of theamplifier E is then used to overcome the grid bias on the thyratron,causing the thyratron to conduct. This, in effect, connects the B+supply voltage to capacitor 57 which then charges at a rate determinedby the size of resistance 56 and capacitor 57. The voltage variationappearing across capacitor 57 is applied as an input voltage for theaudio amplifier 30 via capacitor 59 and resistance 60. This voltagevariation is amplified to the coil 27 of speaker 28 where it is thenemitted as a warning sound. The voltage across the capacitor 5'7continues to increase until it is high enough to cause the neon tube 58to conduct. The discharge of the capacitor 57 through the neon tube isalso amplified and emitted as a warning sound via speaker 28. Thyratron5 continues to conduct, again charging the capacitor 57, so that thecycle of operation just described is repeated for so long as thethyratron remains conductive.

In the embodiment of the invention shown in FIG. 3, the transducer isemployed in an electrical circuit which provides a means of detectingand determining whether the pressure at plate 8 of the transducer hasincreased or whether it has decreased and a means for actuating awarning device, water supply controls or other devices which are torespond according to whether the pressure has increased or decreased.

The circuit comprises an audio oscillator, a two-stage amplifier, apush-pull detection circuit, a push-pull amplifier, two relays, and a B+or plate voltage supply. One output terminal of the audio oscillator 81is connected to lead 15 of coil 4 of the transducer. The other outputterminal 82 of the oscillator and lead 16 of coil 4 are connected toground. Lead 18 of coil 7 of the transducer is connected to ground. Thelead 17 of coil 7 is connected via series connected resistance 83 andvariable resistance 84 to the conductor which connects terminal 80 tolead 15 of coil 4.

The grid of a triode vacuum tube 85 is connected via grid limitingresistor 86 to the conductor connecting resistances 83 and 84. Thecathode of tube 85 is connected to ground via grid biasing resistance87, and the plate is connected to the B+ or plate supply voltage viaload resistance 88. The plate is also connected to ground via couplingcapacitor 39 and grid resistance 90.

The grid of a triode vacuum tube 91 is connected via grid limitingresistance 92 to the conductor connecting capacitor 89 to resistance 50.The cathode of tube 91 is connected to ground via grid biasingresistance 93, and the plate is connected to the B+ or plate supplyvoltage via the primary winding 94 of transformer 95.

The secondary winding 96 of transformer 95 has a center tap 97 connectedto ground via resistance 98. Center tap 97 is also connected viacapacitor 99 to the plate of the output tube of the audio oscillator 81.One lead of the secondary winding is connected to the plate of diode100. The other lead of the secondary winding is connected to the plateofdiode 101. The resistance 102 of a potentiometer 103 is connectedbetween the cathode of diode 1'00 and the cathode of diode 101. Themovable contact 104 of potentiometer 103 is connected to ground. Thecathode of diode 100 is also connected via grid current limitingresistance 105 to the grid of a triode vacuum tube 106. Similarly, thecathode of diode 101 is connected via grid current limiting resistance107 to the grid of a triode vacuum tube 108.

The cathodes of tubes 106 and 108 are connected together via resistance109 of a potentiometer 110. The movable contact 111 of the potentiometeris connected to ground. The plate of tube 106 is connected to B+ orplate supply voltage via winding 112 of relay 113. Similarly, the plateof tube 108 is connected to B+ or plate supply voltage via winding 114of relay 115. The normally-open contacts of relays 113, 115 are eachconnected in a control or warning system. Thus, one warning systemcomprises a current source and a bell 116 in series with the contacts ofrelay 113, while the other warning system comprises a current source anda bell 117 in series with the contacts of relay 115.

Operation of the embodiment of FIG. 3 is as follows: When the transduceris placed below the surface of a body of water, plate 8 is moved closerto the tips of core 3 due to the pressure of the water on plate 8.Placing the transducer at a particular depth establishes a certaindegree of magnetic coupling between coil 4 and coil 7 which changes whenthe transducer is moved to a different depth or when the water levelchanges. The audio oscillator output is applied to coil 4 of transducer1 which adds to and subtracts from the flux created by permanent magnet5 which causes permeable plate 8 to vibrate. When plate 8 vibrates themagnetic coupling between coil 4 and coil 7 is varied in response to thevibrations. A voltage is induced in coil 7 which is a function of themagnetic coupling between coil 4 and coil 7 and the change in current incoil 7;

The voltage induced in coil 7 is approximately 180 out of phase with thevoltage which is applied to coil 4 from the audio oscillator 81 viaadjustable resistance 84 and resistance 83. By adjusting resistance 84the voltage across coil 4 and resistance 83 can be set at Zero. Aftersuch an adjustment is made, any change in pressure at plate 8 of thetransducer due to a change in the water level or movement of thetransducer to a diflerent depth results in a change in the voltageinduced in coil 7. The change in the voltage induced in coil 7 causesthe voltage at summing point X to be either in phase or 180 out of phasewith the audio oscillator output, such in phase or 180 out of phasevoltage then being applied as the grid signal of tube 85. Whether theincrement of pressure change was an increase or decrease in pressuredetermines the phase relationship of the voltages.

tube will conduct only when the amplifier signal is 180 out of phasewith the audio oscillator. The potentiometer 103 is used to equalize thecurrent flow through diodes 100, 101.

When diode 100 conducts, the flow of current will be through thatportion of resistance 102 of potentiometer 103 between the cathode ofdiode 100 and ground thus providing the grid signalvoltage for the gridof tube 106. The grid of tube 108 is similarly provided with a gridsignal voltage when diode 101 conducts. The tubes 106, 108 will conductwhen a grid signal is applied to their respective grids. Here again, thepotentiometer 110 is used to equalize the flow of current through tubes106, 108.

Since the coil of relay 113 is in the plate circuit of tube 106, relay113 operates when tube 106 conducts. Closure of the contacts of relay113 completes the circuit containing bell 116. Similarly relay 114operates and bell 117 rings when tube 108 conducts. Thus, one relayoperates in response to an increase in pressure at the plate of thetransducer while the other relay operates in response to a decrease inpressure. Rather than completing a circuit containing a bell as shown inFIG. 3, the relays can be used to control operation of a mechanismdesigned to correct for the pressure changes.

While specific embodiments of the invention have been employed toillustrate the invention, it will be understood that the invention isnot limited to these specific embodiments and that numerous changes canbe made without departing from the scope of the invention as defined inthe appended claims.

What is claimed is:

1. In a versatile communication system for underwater and above surfaceuse, the combination comprising a water submersed transducer, anatmospherically immersed loudspeaker, an audio frequency input sourcefor introducing radio signals and voice messages, and a unitarilyactuated switching means for selectively connecting said input source tosaid loudspeaker in a first position and connecting said input sourcesimultaneously to said transducer and said loudspeaker in a secondposition, whereby the emission of signals originating at the inputsource may be selectively transmitted as sound waves in the air in saidfirst position and as sound waves both underwater and in the airsimultaneously in said second position.

2. The communication system of claim 1, wherein there is a first audioamplifier having an input and an output, said unitarily actuatedswitching means being connected to the input of said first audioamplifier, the output of said audio amplifier being connected to saidloudspeaker in the first position of the switching means and to saidloudspeaker and said transducer in the second position of the Tube 85 isin the first stage of a two stage amplifier I indicated generally at G.The voltage across resistance.

83 and coil 7 which-is applied to the grid of tube85 is amplified andappears across secondary winding'fita of transformer 95.

The center tap 97 of the secondary winding is coupled to the plate ofthe last tube of the audio oscillator 81 via capacitor 99 and is alsoconnected to ground via resistance 98. The voltage at the center tapwith respect to ground thus varies in accordance with the voltagepresent at the plate of the last tube of audio oscillator 81. Dependenton whether the amplified signal was in phase or 180 out of phase withthe audio oscillator voltage, one or the other of diodes 100, 101 willconduct. One

switching means.

3. The communication system of claim 2, wherein said unitarily actuatedswitching means, in a third position connects the transducer to theinput of said first audio amplifier, the" output of said first audioamplifier being connected to said speaker whereby the under water vi-,brations may be emitted only as sound waves in the air.

4. The communication system of claim 3, wherein there is visualsignalling means, and a second audio amplifier having an input and anoutput, said unitarily actuated switching means, in a fourth position,connects the transducer to the input of said second audio amplifier,actuating means connecting the output of said second audio amplifier tothe visual signalling means to actuate said" visual signaling means uponaudio frequency signals from said transducer reaching said second audioamplifier said actuating means connected also to the input of the firstaudio amplifier to emit a signal from said loudspeaker, whereby thewater pressure changes against the submersed transducer cause visibleand audible signals.

(References on following page) Refexenees Cited in the file of thispatent UNITED STATES PATENTS Fessenden Jan. 23, 1917 Spath June 2, 1925Cooke May 16, 1933 Colton Dec. 24, 1935 West July 4, 1939 Bennet Sept.26, 1939 Shaw Oct. 8, 1940 Murphy Apr. 15,1941 Black Nov. 12, 1946 8Trent Feb. 1, 1949 Tiffany Feb. 20, 1951 Garstang Oct. 30, 1951 CampbellAug. 12, 1952 Scott Apr. 12, 1955 Geneslay Apr. 3, 1956 Levy July 17,1956 Kursman July 9, 1957 OTHER REFERENCES Military Specification,MILC-17831A (Ships), Feb. 16, 1956. Fig. 1, Block Diagram (page 21).

1. IN A VERSATILE COMMUNICATION SYSTEM FOR UNDERWATER AND ABOVE SURFACEUSE, THE COMBINATION COMPRISING A WATER SUBMERSED TRANSDUCER, ANATMOSPHERICALLY IMMERSED LOUDSPEAKER, AN AUDIO FREQUENCY INPUT SOURCEFOR INTRODUCING RADIO SIGNALS AND VOICE MESSAGES, AND A UNITARILYACTUATED SWITCHING MEANS FOR SELECTIVELY CONNECTING SAID INPUT SOURCE TOSAID LOUDSPEAKER IN A FIRST POSITION AND CONNECTING SAID INPUT SOURCESIMULTANEOUSLY TO SAID TRANSDUCER AND SAID LOUDSPEAKER IN A SECONDPOSITION, WHEREBY THE EMMISSION OF SIGNALS ORIGINATING AT THE INPUTSOURCE MAY BE SELECTIVELY TRANSMITTED AS SOUND WAVES IN THE AIR IN SAIDFIRST POSITION AND AS SOUND WAVES BOTH UNDERWATER AND IN THE AIRSIMULTANEOUSLY IN SAID SECOND POSITION.